Electrical connector



March 9, 1954 1 R, VlCKERY 2,671,889

ELECTRICAL CONNECTOR Filed April 22, 1948 /4 INVENTOR ATTOR Y PatentedMar. 9, 1954 ELECTRICAL CONNECTOR John R. Vickery, York, Pa., assignerto Aircraft- Marine Products Inc., Harrisburg, Pa.

Application April 22, 1948, Serial N o. 22,630

z claims. 1

This invention relates to insulating terminals of the type broadlydescribed and claimed in an application of William S. Watts, Serial No.732,469, led October 28, 1947, now Re. 23,688, and particularly toconnectors and connections and methods of making the same wherein theinsulating sleeve on the exterior of the connector is expanded toreceive an insulation of larger diameter than the exterior diameter of ametal ferrule on which the insulating sleeve is mounted. As heretoforemade, these insulated connectors have proven highly satisfactory wherethe insulation was no larger than the exterior of the metal ferrule sothat it could be inserted into the insulating sleeve on the connector,e. g. as shown in said patent. It has also been the practice to stretchthese sleeves to a moderate extent in order to receive somewhat largerinsulation. However, because of the requirements of the insulatingsleeve and particularly the necessity of having a very tough plasticresistant to cold plastic flow so that it can transmit without failuresuiiicient pressure to crimp the metal ferrule securely onto a wire,there has been a limit to the amount of stretching or expansion whichcan be eiected without breakage of the insulating sleeves. Thus, it hadbeen found that this could be made only in limited sizes with lightly ormoderately insulated wire and more expensive types of connectors havebeen required for heavily insulated wire.

We have now found that it is possible to introduce any required amountof expansion and stretch into the extended portion of the insulationwithout loosening the insulation on the metal ferrule of the connectorby heating this extended portion of the ferrule substantially to atemperature at which it is softened suiciently to be stretched withoutdanger of cracking. At this temperature, however, the stretchedcondition is not retained but the plastic returns rapidly to a smallerdiameter and therefore, upon initial trial, this method appears to haveno promise. According' to the present invention it has been found thatif the sleeve is cooled the rate of return is gradually decreased and,if cooled to atmospheric temperatures, the expanded form is, forpractical purposes, stable, although it retains its elastic memory andthe sleeve will shrink again upon heating to a temperature at whichsoftening begins. This condition of elastic memory may be desirable inmany cases since it makes possible the gripping of the insulation on awire merely by application of heat, e. g. with radiant infra red lampsor by passing through a blast of hot gas or into a high frequency field.It alsofacilitates mechanical crimping or pressure forming of theexpanded portion of the sleeve onto the insulated portion of the wire.

Where this stretching is undesirable for any reason, it has been foundthat according to the present invention the sleeve may be initiallyformed with a diameter suiiiciently large to receive the insulation, andthe portion over the metal ferrule of the connector may be cold moldedby pressure so as to grip the ferrule while the extended end is leftuncompressed and therefore capable of receiving the insulating portionof the wire.

In the accompanying drawings Fig. 1 is a longitudinal section through aterminal connector provided with an insulating sleeve of tough plasticmaterial.

Fig. 2 is a similar axial section showing the extended portion of thesleeve expanded by means of an anvil or pin which is shown in its finalposition within the sleeve.

Fig. 3 is a similar axial section showing a connector and insulatingsleeve in preliminary assembled relation.

Fig. 4 is a corresponding view of the same showing the sleeve of Fig. 3compressed onto the ferrule.

Fig. 5 shows a complete connection made by use of either of theconnectors of Fig. 2 or Fig. 4.

Fig. 6 shows another type of splicing connector with an insulatingsleeve in process of being applied.

Fig. 7 is a View of the same after application is complete.

Fig. 8 is a similar cross-sectional view of another terminal connectorwith the insulating sleeve initially positioned thereon; and

Fig. 9 is a similar View of the same after expansion of the insulatingsupporting portion.

Referring rst to Figures 1 and 2, the metal portion of the terminal lll,as there shown, may be made by any of the manufacturing methods as wellunderstood in this art, e. g. from copper tubing by flattening andexpanding one end, or from sheet metal by stamping and rolling thelateral portions into a cylindrical ferrule or by deep drawing methods.In any case, the ferrule forming portion l2 is made adjacent the tongueportion if: and over this ferrule forming portion a plastic sleeve i5 isapplied.

In a preferred example the sleeve as applied may be a standard vinylitetubing consisting. for example of vinyl chloride vinyl acetate copolymerhaving about 3-5% acetate and plasticized to a exible and stretchablecondition. In this condition the tubing may be applied over the ferrulemuch as a rubber hose would be applied over a nipple with a slightconstrictive fit so that it can readily be slid in place for subsequentoperation. The tubing is then cut off at a distance beyond the end ofthe metal ferrule portion I2, e. g. as shown in Fig. 1.

The terminal is then baked in an oven with forced convection whereby theplasticizer is volatilized and removed from the sleeve leaving thelatter in a very tough and stiff condition. While still hot, afterremoval from the oven, or after re-heating, e. g. by exposure to infrared radiation, these terminals are driven onto an expanding mandril orpin I8 as shown in Fig. 2, so that it enters into the extended portionII, and thus the desired expansion of the interior bore of the tube isobtained.

The pin I8 is cooled sufficiently during and/or between the stretchingoperations so that while it is pushed into the sleeve it quicklyextracts heat from the sleeve and after a few seconds, e. g. 1A to 1A;minute, the connector may be discharged from the pin in a sunicientlycooled condition to hold its expanded condition. Advantageously, upondischarge from the pins the terminals are immersed in cold water so asto assure that they are well below the temperature at which elasticmemory would result in objectionable return toward the smaller diameter.

Instead of pre-heating the extended portion I1 of the insulating sleeveand forming it on a cold pin, one may practice the invention by using aheated pin and driving it more slowly into the extended end of theplastic sleeve so that its heat may be transmitted into the plastic asit is expanded or the plastic may be spun to the larger diameter using aheated iron to work the plastic outward or exposing it and heatingexternally or internally in other manner while the spinning progresses.

In the case illustrated in Figures 3 and 4 the insulating sleeve I6a isof larger diameter than the ferrule forming portion I2 and instead ofexpanding portion I'I and the portion I5a over the ferrule, portion I2is compressed from its normal diameter as shown in Fig. 3 to a smallerdiameter as shown in Fig. 4 wherein it grips the ferrule portion I2.

ISince the plastic can be more severely deformed under compression thanunder tension without failure, this compression can often be done as acold molding operation. It can be done in confined compression dies orit can be done by spinning. In the latter case, however, heating thetool or the sleeve will facilitate the compression. This compression ofthe sleeve onto the ferrule portion may also be combined with astretching of the extended portion and this in particular enables one toeffect the necessary deformation of the sleeve without heat since thelimited expansion which may be safely permitted as cold deformation maybe given to the extended portion I'I while the portion I5 is compressinga limited safe amount to engage the ferrule portion I2.

In any case the terminal may be applied to an insulated Wire as shown inFigure 5. The end of the wire is first bared by stripping part of theinsulation from the Wire and the bared end of the central connector 22is inserted into the ferrule portion I2 while the end of the insulation24 is inserted into the expanded portion II of the insulating sleeve.Both portions II and I5 are then compressed, advantageously in a fullyconfined compression die, so that the plastic sleeve and the ferruleportion are tightly pressed into permanent engagement with the wire andthe wire itself is compressed and to some extent extruded to give asolid and low resistance connection.

In Figures 6 and '7, I have shown a splice connector of the type used toconnect wires of different sizes. In this case the metal portion of theconnector is formed with ferrules of four different sizes, two toreceive the insulation of the two different sized wires and two centralferrule portions for receiving the bared wires. In this case aninsulating sleeve has been used of inside diameter approximating theoutside diameter of the smaller of the insulation supporting sleeves andthe insulating sleeve |61) is then driven over the larger sleeve eitherwith or without heat, depending upon the extent of expansion required.Subsequently the intermediate portion of the sleeve IBb is pressed, asin the case described in connection with Figures 3 and 4, so as tosubstantially fit the exterior of the central wire-receiving ferrules asillustrated in Figure '7, It is not necessary that the interior metalconnector member have ferrules for the insulation support portions ofthe connector and in such case, if only the central ferrules are usedthe sleeve I6b may be made to fit the larger of the two ferrules. Inthis case a cold expansion may be suicient with the smaller insulationsupport and this may be effected at the same time that the compressionto the smaller wire receiving ferrule is made. In this case, however,expansion with the larger insulation support end of the sleeve wouldprobably be too great for cold expansion, and therefore the heating andchilling as described above in connection with Figures l and 2 should beresorted to. The smaller insulation supporting end may also be expandedat the same time in the same manner by such heating, but in that casesuch expansion is most advantageously effected before the compressiononto the smaller ferrule.

It should be understood that the selection and use of suitable plasticsleeves for insulating connectors of this type and their treatment bybaking or other methods to produce the desired stiffness and toughness,and the materials and form of the connector and particularly of theferrule forming portion Whether completely cylindrical or partiallycylindrical or U-shaped, etc., are all matters previously invented anddisclosed to the art, and may be varied as desired without departingfrom the scope of the present invention.

What is claimed is:

1. An electrical connector of the type adapted to be crimped onto abared portion of an insu lated wire which comprises a malleable metalferrule adapted to have said bared wire portion inserted therein; and atough malleable extruded plastic insulating sleeve tightly fitted aroundthe outside of said ferrule; said plastic sleeve also extending for asubstantial distance beyond an end of said ferrule; said sleeve beingcomposed of a stifiiy flexible plastic which is a copolymer of vinylchloride and vinyl acetate and as originally extruded, being of uniformbore throughout, said extended portion of said sleeve being expandedafter extrusion to an internal bore substantially greater than the boreof said sleeve portion fitted over the ferrule whereby to snuglyencompass the insulation of said wire ad jacent to the bared wireportion; said expanded portion of said sleeve having been formed bystretching an end part of said sleeve while it is maintained at anelevated temperature over a forming pin, thereafter cooling said endpart while still stretched over the pin and nally Withdrawing the pin,to thereby produce an expanded end having an elastic memory of itsoriginal extruded bore.

2. An electrical connector of the type adapted to be crimped onto abared portion of an insulated Wire which comprises a malleable metalferrule adapted to have inserted therein said bared Wire portion; atough malleable extruded plastic insulating sleeve tightly embracing theoutside of said ferrule; said plastic sleeve being composed of a stiiilyflexible copolymer of vinyl chloride and vinyl acetate and as originallyextruded, being of uniform bore throughout, said sleeve extending for asubstantial distance beyond an end of said ferrule; said extendedportion of said sleeve being of a substantially larger internal borethan the bore of said sleeve portion embracing the ferrule in order tohave inserted therein the insulation of the wire adjacent to said baredWire portion; said extended portion of said sleeve having been expandedafter extrusion to its larger bore by stretching said extended portionWhile it is maintained at an elevated temperature over a forming pin,then cooling said extended portion While still stretched over the pinand iinally withdrawing the pin, to thereby produce an expanded sleeveportion which has an elastic memory of its smaller original extrudedbore and will tend to shrink more tightly about said Wire insulation.

JOHN R. VICKERY.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 2,110,783 Walker Mar. 8, 1938 20 2,158,044 Haller May 9, 19392,379,567 Buchanan July 3, 1945 2,429,585 Rogoi Oct. 21, 1947

